NL1014355C2 - Process for the preparation of nutrient granules. - Google Patents

Description

PROCESS FOR THE PREPARATION OF NUTRIENT GRANULES 5

The invention relates to a process for the preparation of granules of inorganic nutrients in which the inorganic nutrient is subjected to granulation in the presence of a polysaccharide, Ca ions and NO3 ions. The invention also relates to such granules.

Mineral fertilizers are usually marketed as granules with a grain size of 2 to 5 mm. A large grain size and an even size distribution are important in order to blend the products. However, some single products are only available in powder or crystal form. For the use of blends 20 it is highly desirable if not necessary to have the individual components available in larger, strong particles with a high nutrient content. In addition, due to baking and dust problems, it is also desirable to have the nutrients available in the form of larger particles.

Inorganic nutrients within the scope of the invention are, for example, inorganic salts, in particular sulphates, for example potassium sulphate, magnesium sulphate and ammonium sulphate; and chlorides, for example sodium chloride and potassium chloride; nitrates, for example potassium nitrate and calcium nitrate; or mixtures of these compounds, optionally in combination with other components, for example trace elements Se, Cu or Co, or auxiliary substances, for example clay, which can make the granules even more stable and stronger. A problem with these nutrients is that they are difficult to granulate.

The invention provides a method in which relatively large granules with a relatively high nutrient content can be obtained. These nutrients are commercially available in powder form and can be used as such in the method according to the invention. The combination of a polysaccharide with calcium and nitrate ions ensures a strong gelling and binding character. Neither the presence of calcium ions separately or nitrate ions separately ensure this strong character of the binder.

It is known to compact sulfate powder, for example. The disadvantage of the compacted particles is that they are usually angular and still give rise to dust formation during transport and processing. In addition, for example, ammonium sulfate 20 is also known in crystal form. However, this crystal form is so different from other granules used in bulk blends that good quality blends cannot be made.

The granulation, for example steam granulation, can be carried out in various well-known ways, for example in a pan or drum granulator. Usually, because of the solubility of the nutrients, the choice will be made to granulate nutrients as a solid, (ground) powder, with, for example, water and / or steam.

Preferably a polysaccharide is selected with a combination of high solubility 1014300-3-polysaccharide in water and high viscosity of the polysaccharide. Higher solubility can compensate for a lower viscosity; and vice-versa. Preferably, as little polysaccharide as possible is used because of the cost aspect on the one hand and the need to obtain the highest possible nutrient content in the granule on the other hand. The optimal amount of polysaccharide to be used depends very much on the choice of the polysaccharide and can easily be determined by the skilled person. In practice, the amount of polysaccharide in the nutrient granule will usually be between 0.01 and 10% by weight of polysaccharide, preferably between 0.01 and 3% by weight. It is not necessary that the polysaccharide in completely dissolved form is used in the cannulation. The polysaccharide can also be used as a slurry. Suitable examples of polysaccharides to be used are (pre-gelatinized) potato, wheat or corn starch, arabic gum, cellulose, methyl cellulose and carboxymethyl cellulose. The potato starch preferably consists of partially soluble, pre-gelatinized starch with the starch partially cross-linked by a physical or chemical modification to have better heat and shear resistance during granulation. The amount of (pre-gelatinized) starch to be used will in practice often be higher than the amount of carboxymethyl cellulose to be used.

The amount of Ca ions to be used is preferably greater than 0.05 wt% calculated as Ca in the final product, in particular greater than 0.1 wt%. The amount of NO 3 ions to be used is preferably 10 14 14 6 - 4 - greater than 0.15 wt%, in particular greater than 0.3 wt%, calculated as NO 3 "relative to the total end product The Ca and NO3 ions are preferably added in the form of a solution of Ca (NO3) 2 in water, but they can also be used in the form of other water-soluble salts, for example calcium chloride and sodium nitrate.

The granulation is preferably carried out in the presence of sulfate ions. An increased granulation efficiency is hereby realized. The amount of sulphate ions to be used is preferably greater than 0.1% by weight of SO4 ~ calculated with respect to the total end product.

A preferred embodiment of the method according to the invention is, for example, as follows. First, a solid phase and a liquid phase are prepared. For example, the solid phase contains about 70 to 95 percent of an inorganic salt, about 0 to 15 percent of a sulfate salt, 0.1 to 5 percent of a water-soluble polysaccharide, 0.1 to 5 percent of a water-soluble calcium salt, 0.2 up to 5 percent of a water-soluble nitrate salt and 0 to 5% of a granulation promoting aid, for example clay.

A preferred composition contains 85 to 95 percent inorganic salt, 0 to 5 percent sulfate salt, 1 to 3 percent water-soluble polysaccharide, 0 to 3 percent water-soluble calcium salt, 0 to 3 percent water-soluble nitrate salt, and 0 to 4 percent granulation-assisted vehicle.

For example, the liquid phase contains about 0 to 10 percent polysaccharide, 0 to 15 percent water-soluble calcium salt, and 0 to 15 percent 1014355-5-water-soluble nitrate salt. A preferred composition contains 4 to 8 percent polysaccharide, 8 to 12 percent calcium salt, and 8 to 12 percent nitrate salt. The liquid phase is added to the solid phase in a usable amount. The amount depends on the granularity of the mixture, but in practice it means that the water content of the mixture preferably varies between 4 and 12 percent water. When using more concentrated solutions, extra water or steam can be added. The manner in which the solution is added to the solid mixture is not critical to the practicability of this invention. There is, however, a preference for finely distributing the liquid over the powder mixture in the grain drum. The solution is preferably made by first heating water to 80 ° C and then adding the salts and the polysaccharide while stirring vigorously.

After the granulation, the granules can be dried in a known manner, for example in a rotary drying drum with a warm air flow.

The final moisture of the granules is preferably between 0.7 and 1 percent, since usually a hard and stable grain is obtained.

With the method according to the invention stable, strong nutrient granules are obtained. The size of the particles, after removal of dust and coarse product, is in practice often chosen between 1 and 6 mm, preferably between 2 and 4.7 mm, adapted to the needs in the market. Other dimensions are also possible in principle.

1014 3 b 5 - 6 -

The invention will now be elucidated on the basis of the examples, without, however, being limited thereto.

Example I

Potassium sulfate with a size between 0.1 mm and 1.2 mm was used as the inorganic salt. This salt was mixed intensively with 2% wt. % starch. In some runs, this mixture was supplemented with additional aids such as clay and calcium nitrate. The total amount was six kilograms. The composition of this solid phase is given in Table 1.

The solid phase was wetted in a moving grain drum by spraying a liquid phase. The liquid phase was formulated to provide a moisture content of about 10 wt% water; the composition of the liquid phase in the different runs is also given in Table 1.

After granulation, the granules were dried in a 400 (mm) x 1500 (mm) rotary dryer at a speed of 12 rpm, an air inlet of 400 ° C and this for 20 min. The product which then had a temperature of around 100 ° C and a moisture content less than or equal to 1% by weight was sieved on a 2 and 4 mm sieve.

Table 1 demonstrates the effect that the different solid and liquid phase compositions have on efficiency. The efficiency here is represented by the granulometry of the granules falling from the dryer. The higher the fraction is less than 2 mm, the more product must be returned to the grain drum, the less the (economic) return will be.

As the starch, a potato starch was used consisting of partially soluble pre-gelatinized starch with the starch partially cross-linked. The calcium nitrate contained one and a half moles of water and the calcium chloride contained 2 moles of water.

The solutions were made as follows; Water was heated to a temperature of 80 to 90 ° C. While the liquid was stirred vigorously (mechanical stirrer, 1500 rpm), the binders and / or auxiliaries were added together. The liquid was kept at a temperature of 80 ° C.

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Runs 1, 3 and 4 show that the combination of starch with calcium and nitrate ions yields a good yield. Run 2 shows that it is not the product calcium nitrate but the ions 5 calcium and nitrate that provide the positive combination. This is confirmed in run 6, where only the nitrate ion is present, and thus yields a noticeably lower efficiency. Run 7 shows that only starch as a binder forms few grains of the required size. Run 8 shows that calcium nitrate alone is not a binder.

Run 5 shows that calcium nitrate is preferably added in the liquid phase, since the efficiency of run 5 is lower than in run 4, where the calcium and nitrate ions are released slowly.

Note: To demonstrate that these are indeed hard grains, the breaking strength of the grains in the screen fraction 3.35-4.00 was determined for run 1 and 3.

20 For run 1 the breaking strength was 40 N, for run 3 it was 31 N.

Example II

Potassium chloride was used as the inorganic salt. The test was performed as described in Example I with the compositions listed in Table II.

Ammonium sulfate had a screen range less than 2 mm, with a d50 of 1.1 mm.

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Example III

Potassium sulfate was used as the inorganic salt and CMC (carboxymethyl cellulose) as the binder. The CMC used here was a sodium carboxymethyl-10 cellulose with a viscosity of 2000 mPa.s. at a concentration of 2.0% by weight percent dry matter in water at a temperature of 25 ° C. The test was carried out as described in Example I with the compositions listed in Table III.

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Run 11 shows that the CMC and calcium nitrate combination, when dissolved, yielded a good yield. This is despite the low concentration of CMC. In the absence of calcium nitrate (run 13), the binding force of CMC is minimal.

1014353

Claims (14)

1. Process for preparing granules of inorganic nutrients, wherein the inorganic nutrient is subjected to granulation in the presence of a polysaccharide, Ca ions and NO3 ions. 2. A method according to claim 1, wherein a solution of Ca (NO3) 2 in water is used. A method according to claim 1 or 2, wherein the nutrient is selected from the group of sulfates, chlorides or nitrates. 4. The method of claim 3 wherein the nutrient 15 is selected from the group consisting of potassium sulfate, magnesium sulfate, ammonium sulfate, potassium nitrate, calcium nitrate, sodium chloride and potassium chloride. 5. Process according to any one of claims 1-4, wherein the amount of polysaccharide used is between 0.01 and 10% by weight, based on the total amount of end product. 6. A method according to any one of claims 1-5, wherein a sulphate is also present in the granulation. A method according to any one of claims 1-6, wherein the amount of NO3 ions used is greater than 0.15% by weight calculated as NO3 'relative to the total amount of final product. 8. A method according to any one of claims 1-7, wherein steam granulation is used. Granule obtainable by the method according to any one of claims 1-7. 10143oö -Ιδ- ΙΟ. Granule containing a nutrient, a polysaccharide Ca ions and NO3 ions. The granule according to claim 9 or 10, wherein the amount of Ca ions is greater than 0.05% by weight. The granule according to any one of claims 9-11, wherein the amount of NO 3 ~ is greater than 0.15 wt%. Granule according to any one of claims 9-12, containing sulphate ions. Granules according to any one of claims 9-13, with a particle size between 1 and 6 mm. Granules according to claim 14, with a particle size between 2 and 4.7 mm. 101431.5 COOPERATION TREATY (PCT) REPORT ON THE NEW INTERNATIONAL TYPE IDENTIFICATION OF THE NATIONAL APPLICATION Characteristic of the applicant or of the authorized representative ______4168 EN_. Dutch application no. Filing date 1014355 February 11, 2000 Claimed submission date Applicant (Name) DSM N.V. Date of the request for an international type research question Awarded by the International Research Agency (ISA) to the request for an international type study. SN 34678 EN I. SUBJECT CLASSIFICATION {where different classifications apply, indicate all classification symbols) According to International Classification ilPCI lnt.CI.7: C05G3 / 00 C05C7 / 02 C05D5 / 00 C05D11 / 00 II. FIELDS OF TECHNIQUE EXAMINED __ Minimum Documentation Requested Classification System Classification Classifications_Int.CI.7: C05G C05C Other Documentation Examined The Minimum Documentation Insofar As Such Documents Are Included In The Research Areas II NO EXAMINATION FOR CERTAIN CONCLUSIONS (comments on supplement sheet), v II LACK OF UNIT OF INVENTION (comments on supplement sheet) _ J Form PCT / ISA / 20t (a> 07.1979